Municipality of Murrysville, PA Article IV Stormwater Management Plan Requirements

§ 198-401 General requirements.

No development plan, subdivision plat or land development plan shall be approved; no permit authorizing construction or development issued; nor any earth disturbance activity subject to this chapter shall be initiated or undertaken unless and until a stormwater management plan for such activity is reviewed and approved in accord with the provisions of this chapter.

A. No regulated development activities within the Municipality shall commence until approval by the Municipality of a stormwater management plan which demonstrates compliance with state water quality requirements after construction is complete. Refer to the Regulated Development Activity Table located in Article III of this chapter.[1]

[1] Editor's Note: See § 198-302D.

B. The stormwater management plan must be designed, implemented and maintained to meet state water quality requirements, and any other more-stringent requirements as determined by the Municipality.

C. To control post-construction stormwater impacts from regulated development activities, state water quality requirements can be met by BMPs, including site design and green infrastructure, which provide for replication of preconstruction stormwater infiltration and runoff conditions, so that post-construction stormwater discharges do not degrade the physical, chemical or biological characteristics of the receiving waters. As described in the DEP Comprehensive Stormwater Management Policy (No. 392-0300-002, September 28, 2002), this may be achieved by the following:

(1) Infiltration: replication of preconstruction stormwater infiltration conditions.

(2) Treatment: use of water quality treatment BMPs to ensure filtering out of the chemical and physical pollutants from the stormwater runoff.

(3) Stream bank and stream bed protection: management of volume and rate of post-construction stormwater discharges, using detention/retention and other means, to prevent physical degradation of receiving waters (e.g., from scouring).

D. In the absence of an existing stormwater conveyance or easement, whether natural or man-made, for release of stormwater flow from a development site, an easement must be provided. Information shall be presented as to the ownership, responsible party, and agreement for said easement.

E. The stormwater management plan must meet DEP regulations that require municipalities to ensure design, implementation and maintenance of best management practices ("BMPs") that control runoff from new development and redevelopment after regulated development activities are complete. These requirements include the need to implement post-construction stormwater facilities and BMPs with assurance of long-term operations and maintenance of those BMPs.

F. Evidence of any necessary permit(s), such as Chapter 102 erosion and sedimentation control or Chapter 105 stream encroachment, for regulated development activities from WCD or the appropriate DEP regional office must be provided to the Municipality. The issuance of an NPDES construction permit [or permit coverage under the Statewide General Permit (PAG-2)] may satisfy the requirements of Subsection A above, after review and approval by the Municipality.

G. Appropriate sections from the Municipality's Subdivision and Land Development Ordinance (SALDO),[2] and other applicable local ordinances, shall be followed in preparing the SWM plans.

[2] Editor's Note: See Ch. 201, Subdivision and Land Development.

H. The Municipality shall not approve any SWM plan that is deficient in meeting the requirements of this chapter. At its sole discretion and in accordance with this article, when an SWM plan is found to be deficient, the Municipality may either disapprove the submission and require a resubmission, or in the case of minor deficiencies, the Municipality may accept submission of modifications.

I. Professional certification. The stormwater management plan (including all calculations) must be prepared and sealed by a qualified professional with training and expertise in hydrology and hydraulics. Documentation of qualifications may be required by the Municipality.

§ 198-402 Stormwater management plan contents.

General format. The stormwater management plan shall include a narrative and a set of plan drawings. Refer to checklist Appendix D.[1]

A. A narrative describing the overall stormwater management concept for the project.

(1) A determination of site conditions in accordance with the PA DEP Stormwater BMP Manual. A detailed site evaluation shall be completed for projects proposed in environmentally sensitive areas, such as brownfields.

(2) Runoff calculations. Stormwater runoff design calculations for determining pre- and post-development discharge rates, for designing proposed stormwater control facilities and to demonstrate that the maximum practicable measures have been taken to meet the requirements of this chapter must be submitted with the stormwater management plan. All calculations shall be prepared using the methods and data prescribed by general requirements in § 198-302. Refer to the Acceptable Computation Methodologies Table in Article III, § 198-307, of this chapter.

(a) Runoff volume and rate shall be calculated according to generally accepted methods such as those listed under Stormwater Management Performance Standards, General Standards.[2]

[2] Editor's Note: See § 198-307.

(b) Detention/retention requirements, including volume, routing, etc., for BMPs shall be calculated using commonly acceptable standard method(s).

(c) Water quality calculations shall be determined by using the PA DEP Stormwater BMP Manual 2006, or current edition, Worksheets 12 and 13, or acceptable alternative method by the Municipality.

(3) Expected project time schedule for the installation of all temporary and permanent stormwater control measures and devices. If the development is to be constructed in stages, the applicant must describe how stormwater facilities and BMPs will be sequentially installed to manage stormwater runoff safely during each stage of development.

(4) The effect of the project (in terms of runoff rate, volumes, and water quality) on surrounding properties and aquatic features and on any existing stormwater conveyance system that may be affected by the project.

(5) If appropriate, the narrative should provide justification as to why any preferred stormwater management techniques, such as LID and green infrastructure, as listed in this chapter, are not proposed for use. Refer to the PA DEP Stormwater BMP Manual 2006, or most-recent edition, for a list of acceptable management techniques.

(6) Operation and maintenance program and responsible party(ies) for permanent stormwater facilities and BMPs. Refer to Article VI of this chapter.

B. The stormwater management plan drawings shall be drawn to a scale of not less than one inch equals 100 feet. All sheets shall contain a title block with the name and address of the applicant and designer, scale, North arrow, legend and date of preparation.

(1) Existing and proposed features. The plan shall show the following:

(a) Watershed location. Provide a key map (using USGS topo maps) showing the location of the development site within the watershed(s) and watershed subarea(s). On all site drawings, show the boundaries of the watershed(s) and subarea(s) as they are located on the development site and identify watershed name(s) and subarea number(s). Refer to Appendix A, Watershed Performance District Maps.[3]

[3] Editor's Note: Appendix A is on file in the municipal offices.

(b) Floodplain boundaries. Identify 100-year floodplains on the development site (as appropriate) based on the Municipal Flood Insurance Study maps.

(c) Natural features. Show all bodies of water (natural or artificial), watercourses (permanent and intermittent), swales, wetlands and other natural drainagecourses on the development site, or which will be affected by runoff from the development.

(d) Soils. Provide an overlay showing soil types and boundaries within the development site (consult WCD, SCS and U.S. Geological Survey for information).

(e) Contours. Show existing and final contours at intervals of two feet; in areas with slopes greater than 15%, five-foot contour intervals may be used.

(f) Land cover. Show existing and final land cover classifications, including existing and proposed improvements, as necessary to support and illustrate the runoff calculations performed.

(g) Drainage area delineations. Show the boundaries of the drainage areas and points of interest employed in the runoff calculations performed.

(h) Utilities and easements. Show any existing utilities, stormwater management or drainage controls and/or structures, such as sanitary sewers, water, gas, electric, telecommunications, storm sewers, swales, culverts, and any easements, which are located on the development site, or which are off site but may be affected by runoff from the development.

(2) Proposed stormwater facilities and BMPs. All proposed stormwater runoff control measures must be shown on the plan, including methods for collecting, conveying and storing stormwater runoff on site, which are to be used both during and after construction. Erosion and sedimentation controls shall be shown in accordance with applicable Municipality and WCD requirements. The plan shall provide information on the exact type, location, sizing, design and construction of all proposed facilities and relationship to the existing watershed drainage system.

(a) If the development is to be constructed in stages, the applicant must demonstrate that stormwater facilities will be installed to manage stormwater runoff safely during each stage of development.

(b) A schedule for the installation of all temporary and permanent stormwater control measures and devices shall be included in the narrative and shown on the site plan.

(c) Operation and maintenance program and responsible party(ies) for permanent stormwater BMPs. Refer to Article VI of this chapter.

(3) Easements, rights-of-way, deed restrictions. BMPs and stormwater management facilities that provide control for more than one lot shall be located on a separate dedicated lot or in an easement. All existing and proposed easements for any BMPs and stormwater management facilities and controls for access, inspections, maintenance, repair, preservation and use shall be shown on the plan and, if required, dedicated to the entity, association or person required. The easement and the purpose for the same shall be set forth on the plan and in the agreement required by this chapter.

[1] Editor's Note: Appendix D is on file in the municipal offices.

§ 198-403 Other permits/approvals.

A list of any approvals/permits relative to stormwater management that will be required from other governmental agencies (e.g., Chapter 102, Erosion and Sedimentation Control, PennDOT HOP, Chapter 105, Water Obstruction and Encroachment Permit, from PA DEP) and anticipated dates of submission/receipt should be included with the stormwater plan submission. Copies of permit applications may be requested by the Municipality where they may be helpful for the plan review.

§ 198-404 Operation and maintenance plan.

The application shall contain a proposed operation and maintenance plan (O&M) for all stormwater control facilities in accordance with the following and as described in Article VI of this chapter:

A. Identify the responsible party and their responsibilities as described in Article VI, § 198-601 (e.g., Municipality, property owner, private corporation, homeowners' association or other entity).

B. Include an operation and maintenance plan for all stormwater facilities, outlining the routine maintenance actions and schedules necessary to ensure proper operation of the stormwater control facilities as described in Article VI, § 198-602.

C. Submit any legal agreements required to implement the maintenance program and copies of the maintenance agreement as required by this chapter. Refer to Article VI, § 198-603.

D. Identify method of financing continuing operation and maintenance if the facility is to be owned by other than the Municipality or a governmental agency. Refer to Article VI, § 198-604.

§ 198-405 Financial guarantees.

Submit financial guarantees in accordance with the provisions of this chapter. Refer to the Appendix.[1]

[1] Editor's Note: The appendix is on file in the municipal offices.